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Bulk and nanosized pyrochlore materials Ln{sub 2}ZrTiO{sub 7} (Ln=La, Eu, Dy, Gd and Sm) have been prepared by the sol-gel method. All the samples were characterized by powder X-ray diffraction, Raman and X-ray photoelectron spectroscopy. Magnetic susceptibility ({chi}) measurements of Gd{sub 2}ZrTiO{sub 7}, Sm{sub 2}ZrTiO{sub 7} and Eu{sub 2}ZrTiO{sub 7} were carried out by vibrating sample magnetometer in the temperature range 2-320 K. The variation of {chi}{sup -1} (or {chi}) with temperature of Gd{sub 2}ZrTiO{sub 7}, Sm{sub 2}ZrTiO{sub 7} and Eu{sub 2}ZrTiO{sub 7} follows the Curie law, intermediate formula and the Curie-Weiss law, respectively. From the linear portion of {chi}T vs. T{sup -1} plot of Eu{sub 2}ZrTiO{sub 7} from 2 to 15 K, the classical nearest neighbor exchange (J{sup cl}) and dipolar interactions (D{sub nn}) are obtained. The XPS of Ln{sub 2}ZrTiO{sub 7} (Ln=La, Eu, Dy and Gd) gave characteristic peaks for Ln, Ti, Zr and O. The satellite peaks are observed only for 3d La of La{sub 2}ZrTiO{sub 7}. -- Graphical abstract: Sm{sub 2}ZrTiO{sub 7} does not follow the Curie or the Curie-Weiss law. The effective magnetic moment is found to be 0.768 BM (at 300 K), which is smaller than the free ion moment 1.3-1.4 BM. Display Omittedmore » Research Highlights: {yields} Bulk and nano Ln{sub 2}ZrTiO{sub 7} (Ln=La, Eu, Dy, Gd and Sm) have been prepared by the sol-gel method. {yields} The broad Raman lines are attributed to cation disorder and small crystallite size. {yields} XPS of Ln{sub 2}ZrTiO{sub 7} exhibit characteristic X-ray photoelectron spectral features. {yields} Magnetic moment of Gd{sub 2}ZrTiO{sub 7} is obtained from magnetic susceptibility and ESR spectra.« less

The results of a Mossbauer study on the effect of substitution of Al3+, Ga3+, and Cr3+ in ferromagnetic FeBO3 close to the Tc are presented. The Curie temperatures of FeBO3, Fe0.9Al0.1BO3, Fe0.9Ga0.1BO3, and Fe0.9Cr0.1BO3 have been determined to be 352, 317, 319, and 335 K, respectively. “Anomalous” spectra have been found to appear just 1° below the Tc for FeBO3, but 15° below the Tc for substituted borates. The inadequacy of static models in explaining these spectra has been pointed out. These spectra have been simulated using relaxation models and estimates of activation energy obtained for spin-flip processes. The results are attributed to dominant superparamagnetic relaxation effects due to the presence of clusters. Mossbauer spectra of FeBO3 substituted by a magnetic ion, viz., Cr3+, are found to differ significantly from those of the above-mentioned samples.